Field of the Invention
The present invention relates to an engagement position storage device that stores an engagement position of a clutch, and a brake system including the same.
Background Art
Conventionally known hydraulic disk brakes to be installed in a vehicle such as an automobile include a disk brake equipped with a parking brake mechanism.
Such a disk brake for use as a usual brake propels a piston in a cylinder by hydraulic pressure and presses a brake pad against a disk rotor, thus generating a braking force. For use as a parking brake, the disk brake rotates a rotating member of a ball-and-ramp mechanism (rotation-linear motion conversion mechanism) by an electric motor via a reducing mechanism to linearly move a linear motion member and move a piston forward, and so press a brake pad against a disk rotor, thus generating a braking force.
Such a hydraulic disk brake equipped with a parking brake mechanism has been requested to deactivate the parking brake promptly and so start a vehicle smoothly.
Japanese Laid-Open Patent Publication No. 2011-214647 (Patent Document 1) discloses a technique of releasing a parking brake promptly, including: determining the presence or not of a parking brake release request by a parking brake switch and the necessity or not of parking brake release by pressing down on an accelerator pedal; and in the case of the presence of a parking brake release request or the detection of pressing-down of an accelerator pedal of a certain amount or more, rotating a rotating member in the same direction as in the parking brake operation by an electric driving mechanism, thus directly moving a ball from a shallowest part of a beveled groove to an adjacent deepest part of the beveled groove.
This technique, however, has a problem of, for automatic release of the parking brake in response to the confirmed starting operation such as activation of an accelerator pedal by a driver, especially for rapid starting of a vehicle equipped with a manual transmission, it takes time to remove a braking force completely after starting of the releasing of the parking brake, and so it has difficulty to release the parking brake completely at a sufficient speed necessary for smooth starting of the vehicle.
To solve such a problem, Japanese Laid-Open Patent Publication No. 2006-528581 (Patent Document 2) discloses a technique of releasing a brake device equipped with an electric parking brake mechanism in response to a confirmed staring operation, in which the releasing timing thereof is specified depending on at least one measured parameter of a clutch engagement operation.
According to the technique disclosed in Patent Document 2, the operating timing of the clutch is confirmed by the engine speed or by the detection of a change in engine torque or a change in acceleration of the vehicle, whereby in the case of rapid starting of a vehicle equipped with a manual transmission as well, the releasing of the electric parking brake can be controlled finely for smooth starting of the vehicle.
The acceleration of a vehicle, however, may change due to factors other than the starting of the vehicle by a clutch engagement operation, such as vibrations induced internally or externally of the vehicle or inclination of the road surface. As such, the technique disclosed in Patent Document 2 may erroneously determine, as a clutch engagement position, the clutch position where acceleration changes due to a factor other than the starting of the vehicle by a clutch engagement operation, and so fail to detect the clutch engagement position of the vehicle finely. Automatic releasing of the braking force based on such a clutch engagement position performed at a position immediately before the clutch engagement position may erroneously release the braking force at a position away from the actual clutch engagement position, thus failing in smooth starting of the vehicle.